Warning light when main lights are on

[Tom and Maria]

Long time no post - embarrassed to say my minor has been off the road for a year needing welding to rear spring hangar. Any way...

My mum's minor has a problem I'm struggling to puzzle out; electrics are generally a mystery to me. The problem is that the ignition warning light comes on when you put the lights on. What could this be? A short in the circuit? All of the lights are working. Red light stays off when braking/ indicating, so seems to be located in main lighting circuit. Red light comes on with sidelights and stays on with main beam. Car is 1962 with nice small sidelights and combined brake/ indicators with red lenses.

She's had problems with the battery getting flat, which I guess is connected I.e. Not charging when lights are on.

Any suggestions of where to begin diagnosis? I have a weekend with the car at the end of June so hope to get stuck in and fix then.

Any thoughts appreciated.

Tom

[simmitc]

Probably the speedo illumination bulb has been put in the wrong hole to light up the ignition light. If you use the slide switch under the dash to turn off the instrument illumination you will probably find that your errant light goes out.

If that bulb is in the wrong holder then others probably are too. The wiring diagram should tell you which colour wires are which lamp, so it's just a question of getting them in the correct hole. If a previous owner has changed the wiring then it's trial and error to see which bulb does where.

[bmcecosse]

As above - bulb holder in wrong hole..... Speedo out for a look. It's a red/white single wire to the speedo lights.

[Trickydicky]

From what you describe it sounds like a charging problem to me, is it a dynamo or alternator?
With the lights on when you rev the engine do the lights get brighter? With a multimeter connected across the battery when you Rev the engine does it read around 13.8v when set to volts dc on the meter?

[oliver90owner]

The 'ignition warning light' should be illuminated with the engine stopped and ignition turned on. A simple way to sort out whether in the corect position (not to be mixed up with the oil pressure light). If It is coming on at times other than tick over, it rather idicates the generator is not charging ( it is actually a charge indicator rather than an 'ignition light'.

The idea of it being an 'ignition light' was for those that left the key turned on while the engine was not running - the coil, being an inductive load normally, would revert to a resistive load and drain the battery over a relatively short period or cook the coil, as it would be dissipating rather more power than with the engine running if the contact breaker happened to be closed (which is likely, as the dwell angle needs to be sufficient for the coil to gain sufficient energy before the next spark).

RAB

[GBond]

It seems your dynamo/alternator isn't charging properly.

Is the belt slipping?

As above check the voltage across the battery when revving the engine.

If still a dynamo, sometimes the regulator can go just a bit out of adjustment, and either charge too much or too little. This can be fixed turning the adjustment screw a little until the light goes off.

[bmcecosse]

" Red light comes on with sidelights " does NOT suggest a charging problem - the sidelights take very little current. Worth checking the belt of course - but I do think it is simple bulb in wrong hole. Does the red light come on when you first switch on the Ign - before starting the car ???

[simmitc]

Yep, it's so simple to check. As I said originally, just turn the instrument lights off (slide switch under dash below main light switch). If your errant light goes out then problem identified. If the switch does not make any difference then nothing lost, but you haven't got involved in loads of unnecessary tests. 3 seconds and you've got your answer without even lifting the bonnet.

[myoldjalopy]

May be two problems here - bulb in wrong place in speedo, BUT if battery is ALSO routinely going flat, then either it is not holding its charge, or is not being charged properly. Quick check - slacken off dynamo fixings, remove fan belt and open regulator box. As you face the car, the cut out (which enables the dynamo to connect to the battery when it is charging 1.e. engine running above idling speed) is the right hand of the two bobbins. With ignition on, press this contact down - if the dynamo is OK it will run as a motor. If it doesn't, suspect dynamo. If it does run, check condition of battery. If battery OK, then probably control box failing. Of course, check all dynamo electrical connections as well - and the fan belt, as stated above. Poor connections and a slack belt will cause charging to fail.
And if you have an alternator, forget everything I said about this test!!

[bmcecosse]

I have always hesitated to suggest this test - but have of course done it myself often in the past. Having closed the contact physically , and the dynamo is whizzing round happily - you need to either prise the contacts apart again - or disconnect the battery, when the contacts should fall open by themselves......

[GBond]

This has been mentioned, but perhaps not explained fully...

The speedo has four warning lights (ignition, high beams, oil pressure, oil filter) and another two bulbs for illuminating the speedo.

The four warning lights should have a small tube over them or otherwise when the speedo is illuminated some light can seep in and create the impression that the warning light is on. Simmitc recommended using the under dash switch to check if this is the case. The bulb could be in the right place, but missing the "tube". Your battery going flat is another problem if this is the case.

[myoldjalopy]

Having closed the contact physically , and the dynamo is whizzing round happily - you need to either prise the contacts apart again - or disconnect the battery, when the contacts should fall open by themselves......

Curious......I don't remember having to do this when I have used this test.........what would cause the points to 'stick' together? It is just 12 v flowing from the battery to the dynamo.....not a higher charge from the dynamo causing the points to close.

[bmcecosse]

Exactly - the current pulls the contact in and holds it. So either 'prise', or pop the battery connection off - or pull the wire off the dynamo of course.

[Tom and Maria]

Thanks for all the hints everyone. I'm going to be with the car later in the month and will investigate further then. From memory, the ignition has the correct bulb attached an comes on as usual before starting the engine. Also from memory, the car has an alternator.

Will post an update when I'm able...

Best wishes,

T

[bmcecosse]

Well -it helps/saves everyones time if we get all the facts at the beginning...... Probably loose belt - or knackered alternator then.